For many years, emergency call services have been implemented in Europe, North America and other jurisdictions. Generally, these emergency call services provide a 3-digit emergency number (e.g., 9-1-1 in North America and 1-1-2 in Europe) that can be used to connect emergency callers with appropriate public resources such as emergency responders. The goals of such systems generally include routing the emergency call to the appropriate call center (Public Safety Answering Point (“PSAP”) in North America) for the location of the call, providing a call back number to the call center, and providing an accurate location to the call center to assist in dispatching.
Emergency call services were first deployed in wireline networks. Because wireline phones were essentially immobile, the caller's phone number could be readily used to look-up the location for the call. The location could be loaded into an automatic location information database (“ALI”) by a local exchange carrier, a mobile switching office (“MSO”), or another party. That location could be used to route the call to the appropriate call center and to provide a location to the call center. More specifically, the phone number could be used both to query a routing database to obtain the emergency service number (“ESN”) of the appropriate call center for routing the call through a selective router to the appropriate PSAP over telephony infrastructure (e.g., a time-division multiplexing (“TDM”) trunk). The phone number could also be used to query the ALI using customer premise equipment (“CPE”) at the PSAP, typically using E2 or PSAP to ALI message (“PAM”) protocol. The ALI is generally queried after the call has been routed to the call center and the responsive ALI record (e.g., including a street address of the caller) can then be delivered to the call center and matched to the call taker who is handling that call such that the location information from the ALI may be displayed at the CPE. In this regard, the address may not arrive at the call center until well after the arrival of the call which may cause a delayed dispatching response.
As wireless telephones gained widespread adoption, the FCC (in the United States) required emergency services for wireless networks. This was implemented via a series of mandates addressing speed and accuracy of location information required for emergency calls with respect to both call routing and providing location information to call centers.
In this regard, a variety of sources of location information may be available. These may be categorized, for example, as cell antenna location information (National Emergency Number Association (“NENA”) Phase I) and mobile unit location information (NENA Phase II). Cell antenna location information relates to the network equipment handling the call and includes cellID and cell sector information. For example, if a cell tower includes a three sector antennae, it may be possible to identify the sector handling the call, thereby locating the mobile unit to an area roughly corresponding to one-third of the geographic coverage area of the tower (ignoring geographical and radio interference issues). Mobile unit location information corresponds to determination of the actual location of the mobile unit, generally as geographical coordinates or a geocode. Methods for acquiring such Phase II data include network triangulation technologies (e.g., TDOA, AOA, strength of signal, etc.), satellite technologies (GPS, GNSS, etc.) and others.
More recently, the FCC (in the United States) has mandated emergency call services for VoIP, at least when bi-directional voice calls are supported. Such VoIP calls may be placed from a substantially immobile computer, mobile data unit, or VoIP phone. There are a number of difficulties relating to deployment of emergency call services for VoIP including locating the unit and call center compatibility. A number of technologies are available or under development for VoIP unit location including GPS, hotspot location, wireless triangulation, node mapping, and others. Call center compatibility remains a technological and practical impediment as many legacy call centers (i.e., legacy PSAPs such as those equipped for enhanced 9-1-1 (“E911”)) are not equipped to handle VoIP calls.
Emergency call routing also remains problematic for mobile units including wireless units and nomadic VoIP units. As noted above, location is generally used twice in connection with an emergency call; coarse location (e.g., Phase I data) for routing and specific location (e.g., Phase II data) for dispatching. In VoIP contexts, it has been challenging to provision even coarse location at call time for routing to the appropriate call center. Even in wireless networks routing errors occur. In particular, call routing is generally executed based on communications network-based data, for example, antenna location and cell sector information. Cell sector boundaries do not always match call center boundaries and, for a variety of reasons, a call is not always handled by the closest call center. Moreover, if the call is routed to the wrong call center, the actual mobile unit location information (delivered later to the correct call center) may never reach the dispatcher. Many challenges thus remain for wireless and VoIP emergency service call handling.
Typically, VoIP calls are routed to a VoIP gateway or call server which sends a request to a VoIP positioning center (“VPC”). The VPC contains a database (e.g., a subscriber line database (“SLDB”)) of known VoIP phone locations and associated uniform resource identifier (“URI”) numbers which may have been manually entered by a network administrator, for example. The VPC may use the stored location information to determine an appropriate contingency resource number (“CRN”) and PSAP for routing the call which are returned to the VoIP gateway. The VPC stores the automatic number identification (“ANI”) and ALI for the VoIP phone and loads a shell record using pseudo-ANI (“p-ANI”) into an ALI database while also mapping the p-ANI to the corresponding ANI. The call is sent to an emergency services gateway (“ESGW”) by the VPC using the CRN (or emergency services routing number (“ESRN”)) with the p-ANI. The ESGW connects the call to the appropriate selective router using the CRN (or ESRN). The selective router uses the ESN to route the call to the PSAP. Using pseudo-automatic number identification (p-ANI), the PSAP is able to query the VPC to obtain the ANI and ALI information stored for the relevant VoIP phone.
In a somewhat similar fashion, mobile 9-1-1 calls (e.g., those originating from mobile phones) are routed to a mobile switching center (“MSC”). The switching center may send the ANI of the device to a mobile positioning center (“MPC”). The MPC loads a shell record into an ALI database using a p-ANI that is specific to a PSAP. The shell record points the PSAP back to the MPC dynamic ALI database (e.g., one maintained by the carrier) for an actual address. The MPC or wireless provider may deploy a position determining entity (“PDE”) for use with antenna towers. At call time, the PDE may send sector information or other location data to the MPC. The MPC may then map the p-ANI to the ANI and return an ESN to the MSC. Using the ESN, the MSC routes the call, based on the sector information, to a selective router with the p-ANI. The selective router delivers the call to the PSAP with the p-ANI information. The PSAP then queries a static ALI over E2 or PAM protocol for the record associated with the p-ANI. Based on the shell record, the PSAP (or the static ALI) may query the dynamic ALI of the MPC over E2 or PAM such that the MPC dynamic ALI may return the sector information to the PSAP. Upon subsequent requests from the PSAP (“re-bids”), the MPC may return more accurate location information as it becomes available over time. This process may cause delays in receipt of accurate location information at the PSAP.
In addition, emergency call handling systems are struggling to accommodate emerging technologies. As noted above, VoIP units are proliferating and some proposals for addressing emergency calls for VoIP units would entail substantial upgrades to call centers and other equipment. At the same time, many jurisdictions are moving towards deployment of next generation (“NG911”) systems that may require changes to legacy call centers. More generally, there is a desire to accommodate texts, images, video and universal call-back number availability, as well as handling emergency calls from sensors and other automated systems, to improve call center functionality. All of these competing opportunities and interests have the potential to result in paralysis as it is unclear how to proceed with development of emergency call systems that meet the needs of emerging technologies in a cost-effective manner.